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# -*- coding: utf-8 -*-
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at
Outputter to generate C++ code for metrics.
import json
import jinja2
from glean_parser import metrics, util
from util import generate_metric_ids, generate_ping_ids, get_metrics
def cpp_datatypes_filter(value):
A Jinja2 filter that renders C++ literals.
Based on Python's JSONEncoder, but overrides:
- lists to array literals {}
- strings to "value"
class CppEncoder(json.JSONEncoder):
def iterencode(self, value):
if isinstance(value, list):
yield "{"
first = True
for subvalue in list(value):
if not first:
yield ", "
yield from self.iterencode(subvalue)
first = False
yield "}"
elif isinstance(value, str):
yield '"' + value + '"'
yield from super().iterencode(value)
return "".join(CppEncoder().iterencode(value))
def type_name(obj):
Returns the C++ type to use for a given metric object.
if getattr(obj, "labeled", False):
class_name = util.Camelize(obj.type[8:]) # strips "labeled_" off the front.
label_enum = "DynamicLabel"
if obj.labels and len(obj.labels):
label_enum = f"{util.Camelize(}Label"
return f"Labeled<impl::{class_name}Metric, {label_enum}>"
generate_enums = getattr(obj, "_generate_enums", []) # Extra Keys? Reasons?
if len(generate_enums):
for name, _ in generate_enums:
if not len(getattr(obj, name)) and isinstance(obj, metrics.Event):
return util.Camelize(obj.type) + "Metric<NoExtraKeys>"
# we always use the `extra` suffix,
# because we only expose the new event API
suffix = "Extra"
return "{}Metric<{}>".format(
util.Camelize(obj.type), util.Camelize( + suffix
return util.Camelize(obj.type) + "Metric"
def extra_type_name(typ: str) -> str:
Returns the corresponding Rust type for event's extra key types.
if typ == "boolean":
return "bool"
elif typ == "string":
return "nsCString"
elif typ == "quantity":
return "uint32_t"
def output_cpp(objs, output_fd, options={}):
Given a tree of objects, output C++ code to the file-like object `output_fd`.
:param objs: A tree of objects (metrics and pings) as returned from
:param output_fd: Writeable file to write the output to.
:param options: options dictionary.
# Monkeypatch util.snake_case for the templates to use
util.snake_case = lambda value: value.replace(".", "_").replace("-", "_")
# Monkeypatch util.get_jinja2_template to find templates nearby
def get_local_template(template_name, filters=()):
env = jinja2.Environment(
loader=jinja2.PackageLoader("cpp", "templates"),
env.filters["camelize"] = util.camelize
env.filters["Camelize"] = util.Camelize
for filter_name, filter_func in filters:
env.filters[filter_name] = filter_func
return env.get_template(template_name)
util.get_jinja2_template = get_local_template
get_metric_id = generate_metric_ids(objs)
get_ping_id = generate_ping_ids(objs)
if "pings" in objs:
template_filename = "cpp_pings.jinja2"
if objs.get("tags"):
del objs["tags"]
template_filename = "cpp.jinja2"
objs = get_metrics(objs)
template = util.get_jinja2_template(
("cpp", cpp_datatypes_filter),
("snake_case", util.snake_case),
("type_name", type_name),
("extra_type_name", extra_type_name),
("metric_id", get_metric_id),
("ping_id", get_ping_id),
("Camelize", util.Camelize),